北密歇根大街875号，原约翰•汉考克中心，是全球首座综合功能大厦，也是建筑师Bruce Graham和结构工程师Fazlur Khan密切合作创造的建筑地标。这座大厦仍是理想合作关系的典型作品，也是SOM在众多设计领域保持领先的重要原因。
875 North Michigan Avenue, formerly known as John Hancock Center, the world’s first mixed-use tower, is an architectural icon representing the close collaboration between architect Bruce Graham and structural engineer Fazlur Khan. The building remains an archetype for the collaborative ideal that continues to make SOM a leader in a wide spectrum of design disciplines.
▼项目鸟瞰，aerial view © SOM
Known locally as “Big John,” the tower is situated on North Michigan Avenue in a prestigious district with expensive apartments, shops, offices, hotels, restaurants, and art galleries. The wish to continue this mixture initially gave rise to the idea of building a 70-story apartment tower and a 45-story office tower. But the two towers would have occupied most of the site and would have impaired each other’s privacy and daylight conditions. Moreover, the lower-level apartments would have suffered from noise nuisance from the street. It was therefore decided to construct a single tower where the offices would be on the lower floors and the apartments on the higher levels.
▼位于北密歇根大街的繁华区域，situating on North Michigan Avenue in a prestigious district © SOM
▼沿湖立面，facade along the lake © SOM
The tower’s tapered shape was chosen in order to match the different floor space requirements that decrease from bottom to top — from the entrance and commercial zones at the base to the clusters of small apartments at medium height and finally to the large apartments on top, where relatively less space is needed for ancillary rooms with artificial lighting.
▼楼身渐收，tower tapering from bottom to top © SOM
▼中上部为公寓，apartments at medium and top © SOM
Structurally, the exterior members of the steel frame represent a tube where the necessary stiffness is provided by diagonal members and by those structural floors that coincide with the intersections of the diagonals and the corner columns. In keeping with the functional organization, this tubular body has its largest cross-section where the stresses caused by wind forces are greatest. Steel consumption, amounting to about 30-pounds-per-square-foot of floor space, was no greater than for a 50-story conventional tower.
▼钢框架，对角分布的钢材与角柱交汇，steel frame，intersections of the diagonals and the corner columns © SOM
▼细节，details © SOM
875 NORTH MICHIGAN AVENUE – STRUCTURAL ENGINEERING
▼框架示意，frame diagram © SOM
A historic collaboration between architects and structural engineers, the 100-story 875 North Michigan Avenue (formerly John Hancock Center) represents the first use of the exterior diagonalized tube structural system, which was developed specifically for this building. Originally planned to be two separate towers, the new structural system allowed for an efficient and economic mixed-use structure that provides more open space at the site. The gross floor area of 2.8 million square feet includes parking, commercial, office, and residential functions. The diverse programming was made possible by the tower’s tapered shape, which creates floor plates of varying sizes to accommodate different functions.
▼项目远观，distant view © SOM
▼对角化外筒结构体系，exterior diagonalized tube structural system © SOM
▼立柱、对角线和拉杆清晰地融入建筑表达中，clarity of the columns, diagonals, and tie members was incorporated into the architectural expression © SOM
An evolution from the framed tube system, the exterior diagonalized tube system allows for wider column spacings and, in turn, larger windows typical of steel construction. The exterior frames act as bearing walls, with gravity loads being uniformly distributed among columns, and lateral loads producing uniform forces in the windward and leeward columns. The X-bracing is generally 20 stories high. A secondary spandrel beam system infills the bracing panels. The clarity of the columns, diagonals, and tie members was incorporated into the architectural expression for which the building remains known and relevant decades after its completion.
▼夜景鸟瞰，aerial view at night © SOM
服务： 结构 + 土木工程、高层建筑
Location: Chicago, Illinois
Project Completion: 1970
Site Area: 104,000 ft2
Project Area: 2,800,000 ft2
Number of Stories: 100
Building Height: 1,127 ft
Market: Commercial + Office, Mixed Use, Residential
Service: Structural + Civil Engineering, Tall Buildings
50 Significant Structures in 50 Years
Structural Engineers Association of Illinois
Architectural Award of Excellence
American Institute of Steel Construction